Back-heat boiler



United States Patent O 3,316,886 BACK-HEAT BOILER Edouard Rud'ekiel, 5 Rue G. Thiriart, Liege, Belgium Filed Oct. 23, 1965, Ser. No. 503,403 Claims priority, application Belgium, May 19, 1965,

s claims. (el. 122-379) This invention relates to maintenance of tubes particularly in back-heat boilers, economisers and superheaters.

Some boilers, including back-heat boilers, economisers land superheaters, may have a heating surface in the form of rows of serpentine tubes suspended in the flue passages for hot smoke. The tubes acquire a considerable load of dust which must be removed regularly to ensure satisfactory heat exchange. One way of cleaning these serpentine tubes is to introduce between some tube rows fire irons or poker-like elements or the like which can 'be operated either manually or mechanically. One of the known mechanical cleaning systems uses reciprocable pokers or the like which can have an ovoid head; the same applies to the tubes, first an impact, then a force tending to separate the tubes from one another, in order to vibrate and thus clean the tubes. Since the tubes of back-heat boilers, economisers and superheaters deal with hot gases and therefore experience expansions which may cause considerable distortions, the distorted tubes may come into a position on the path of the pokers or the like because, Whether manual or mechanical pokers are used, their introduction into the tube-containing flues or passages is by way of apertures which are bound .to be small; consequently, it is impossible to have a clear view of the path followed by the front end -of the poker. Collisions therefore occur; in the case of a manual poker the collisions are a nuisance and can be stopped immediately the resistance of the tube is felt, but consequences may be serious with pokers operated mechanically by a rnechanical system which is blind and does not feel the tube, the usual result being that the poker stops only after having produced serious distortions which may be such -as to pull the tubes out of their mounting.

This invention obviates these disadvantages and aims to provide a safety system for keeping some tubes forming the heating surface away from the path of the front tip of the poker, to ensure that the poker tip cannot. push and distort or pull out any of these tubes when the poker is introduced between the tube rows. The safety system according to the invention comprises means for keeping the tubes apart, between which tubes the cleaning poker or the like is introduced so that such tubes are kept away from the path of the poker although the cleaning action thereof is retained. Preferably the means for keeping the tubes apart from one another take the form of a rigid bar or the like which is, as a rule, disposed horizontally slightly above or below the poker path. If there are a number of poker entry orifices one such bar is provided near each such orifice. The various tube-spacing bars or the like may be interconnected i.e., they form a system resembling -a horizontal coil or serpentine, which system has considerable advantages `when the bars take the form of tubes cooled by a flow of water through them.

The following is a description by Way of example, of a system in accordance with the invention, reference being made to the accompanying drawing, wherein:

FIG. `l is a partial diagrammatic perspective and purely explanatory view ofthe system as used in back-heat boiler tubes, and n FIG. 2 is a partial -diagrammatic view in front elevatlon of the system with some of the front wall removed.

Referring to the drawing, rcoils 3 formed by tubes 3a forming a heating surface -of a back-heat boiler are hung on hangers 2 in a iiue passage chimney (not shown). sion a relatively large 1 for hot smoke going to a The hot gases contain in suspenamount of dust which is deposited on the tubes and may form accumulations detrimental to heat exchange. To clear the dust, the tubes can be cleaned, for instance, by a known mechanical poker 0r the like system, in which event pokers,l such -as partly shown at 4 to 6 and having ovoid heads 4a, 5a, 6a, are introduced between some rows of the tubes 3a at regular time intervals through poke-r orifices, e.g. 7, '8, and 9, pokers being reciprocated by known mechanical means (not shown).

Rigid bars, e.g. 10 or 12, are disposed below the poker orifices and maintain the spacing of the tube rows between which the various pokers move. The bars 10 or 12 are horizontal, take the form of tubes, and are interconnected to form a kind of coil or serpentine in which cooling water ows. The water can be used just to cool the bars, or else it can be the actual -boiler water. The external diameter of the Itubular bars 10 to 12 is such as to provide a passage for the pokers while allowing the boiler tubes to be moved transversely and to be vibrated by lthe pokers.

The system provides a complete safeguard for manual and for mechanical poking; distorted tube-s are prevented from coming into the path of the pokers, and so there is no risk of collision and jamming between the p-okers and the tubes. The lbars may be solid and independent of one another, in which event they are preferably made of a refractory alloy; also, the bars can be disposed above the orices through which the pokers are introduced.

What I claim is:

1. A back-heat boiler having side walls defining a flue passage for hot gas, rows of looped tubes suspended in said flue passage, means supporting the tubes in freehanging loops who-se lower ends are movable relative to each other, said supporting means positioning the tubes in the rows to define a plurality of horizontal clear paths transverse of the rows of tubes, at least one poker movable horizontally between the tube loops along said paths for a distance greater than the distance between the tube loops to knock ash ofi` the tubes, and restraining means spaced between said side walls of the boiler and disposed a `substantial distance below the tops of the tube loops but above the bottoms of the tube loops and limiting the distan-ce the loops may swing transversely of the path of the poker, said restraining means allowing the tube loops lto move freely relatively to said restraining means a substantial distance in a direction transverse to the path of the poker.

2. A boiler as claimed in claim 1, the restraining means having restraining surfaces which 'are Isubstantially parallel to the path of the poker.

3. A boiler as claimed in claim 2, the restraining means comprising a plurality of elongated members substantially parallel to the path of the poker.

4. A boiler as claimed in claim 3, the restraining means being tubular for the passage of cooling water therethrough.

5. A back-heat boiler having side walls defining a tiue passage for hot gas, rows of looped tubes suspended in said tine passage, each tube having la plurality of upright loops lying in a common plane, the said planes of the tubes being parallel to each other and spaced apart, the lower ends of the loops of each tube hanging free and being spaced apart and movable relative to each other in their comm-on plane, means suspending each tube by the upper ends of its loops, said suspending means positioning the tubes in the rows to define a plurality of clear paths transverse of the rows of tubes, at least one poker movable horizontally between the tube loops in a direction substantially perpendicular to said tube planes along said paths for a distance Igreater than the distance between adjacent said tube planes, and restraining means spaced between said side Walls of the boiler and disposed a substantial distance below the tops of the tube loops but `above the bottoms of the tube loops and limiting the distance the loops may move in `said tube planes, said restraining means allowing the tube loops to move freely relative to said restraining means a substantial `distance in said planes.

y6. A boiler as claimed in claim 5, the restraining means having restraining surfaces which are substantially parallel to the path ofthe poker.

7. A boiler as claimed in claim 6, the restraining means `comprising a plurality of elongated members substantially parallel to the path of the poker.

8. A boiler as claimed in claim 7, the restraining means being tubular for the passage of cooling Water therethrough.

References Cited by the Examiner UNITED STATES PATENTS 2,183,496 l2/1939 Peters 122--379 X 2,550,676 5/1951 Dalin 165-84 X KENNETH W. SPRAGUE, Primary Examiner. 

1. A BACK-HEAT BOILER HAVING SIDE WALLS DEFINING A FLUE PASSAGE FOR HOT GAS, ROWS OF LOOPED TUBES SUSPENDED IN SAID FLUE PASSAGE, MEANS SUPPORTING THE TUBES IN FREEHANGING LOOPS WHOSE LOWER ENDS ARE MOVABLE RELATIVE TO EACH OTHER, SAID SUPPORTING MEANS POSITIONING THE TUBES IN THE ROWS TO DEFINE A PLURALITY OF HORIZONTAL CLEAR PATHS TRANSVERSE OF THE ROWS OF TUBES, AT LEAST ONE POKER MOVABLE HORIZONTALLY BETWEEN THE TUBE LOOPS ALONG SAID PATHS FOR A DISTANCE GREATER THAN THE DISTANCE BETWEEN THE TUBE LOOPS TO KNOCK ASH OFF THE TUBES, AND RESTRAINING MEANS SPACED BETWEEN SAID SIDE WALLS OF THE BOILER AND DISPOSED A SUBSTANTIAL DISTANCE BELOW THE TOPS OF THE TUBE LOOPS BUT ABOVE THE BOTTOMS OF THE TUBE LOOPS AND LIMITING THE DISTANCE THE LOOPS MAY SWING TRANSVERSELY OF THE PATH 